1. Field of the Invention
The present invention relates to a method for program debugging, and more particularly, to a method for program debugging which can debug program codes.
2. Description of the Prior Art
In the programming field, the development tools are low level program languages and high level program languages. The text of program codes written in low level languages (e.g. assembly language) is more similar to machine language, but the programming and debugging are not easy. Due to better executing efficiency, low level languages are usually used in basic input/output systems (BIOS) or driver programs.
Take a BIOS for example. After a computer turns on, the main function of the BIOS is to a execute power on self test (POST) to detect whether the settings of peripheral devices are correct, peripheral devices being controlled by the operating system. With the complexity of computers, types of peripheral devices are gradually increasing, such as keyboards, disc units, disc controllers, hard disks, video disc players and so on. Therefore the operation of BIOS becomes more complex. Suppose that the operation of a device on the motherboard is improper or that the programming of BIOS program code contains an error. Since the operating system is not loaded yet, errors are debugged by source codes instead of debug software. This requires more time and a lot of work.
To speed up the debug process, there are two general methods. One method is to insert a debug interface card into the motherboard and to add several diagnosis codes to the BIOS program code. When the BIOS program code is executed at different sections, a diagnosis code would be sent from port 80h to the debug interface card for locking the section. Therefore sections at which errors occur can be found by trapping diagnosis codes.
Please refer to FIG. 1. The other method is called in circuit emulator (ICE). Take a host 7 as the program start, and connect the host 7 and an emulator 8 by the connection port of the host 7 (RS232 or printer parallel port). Also, take a motherboard 9 as the program target, and connect the motherboard 9 and the emulator 8. The host includes assemblers, script files, and so on. The emulator 8 is utilized to simulate a CPU and the emulator 8 is inserted into the CPU slot. Therefore the software of the host 7 can be utilized to control the emulator 8 for remote debugging.
Although the remote debugging provides a good environment for software and hardware, the debug process is still executed by technicians, who execute the script file to BIOS and observe if BIOS is executed as expected. A technician needs to set many breakpoints in places where bugs might occur, and when running into a breakpoint, stop executing the program and determine if the result of the execution is expected. If not, this means that there are bugs in the program codes and the technician must narrow the range to execute the same steps to search for program errors.
However, in the debug of BIOS, besides errors of the program codes, the most important thing is how error handlers of BIOS deal with errors of peripheral devices. For instance, when BIOS detects hardware errors, the motherboard typically provides an alert such as a beep. Due to a large number of peripheral devices, the debug method mentioned above cannot detect if error handlers are missed, and cannot debug all of the error handlers immediately.